Signaling system



K. s. JOHNSON SIGNALING SYSTEM Flled Sept 5 1919 2 Sheets-Sheet 1 Oct. 16, 1923.

Awe/77hr: Ken/767% .5. Johnson by Affy Oct. 16 1923.

K. s. JOHNSON SIGNALING SYSTEM 2 Sheets-Sheet 2 Filed Sept. 5. 1919 Airy Patented Oct. 16, 1923.

UNITED STATES PATENT OFFICE.

KENNETH S. JQHNSON, O-I JERSEY CITY, NEBV ASSIGNOB TO WESTERN ELEC- TRIO COMPANY, INCORPORATED, OF NEW YGRK, N. Y., A CORPORATION OF NEiV YORK.

SIGNALING SYSTEM.

Application filed September To all whom it may concern:

Be it known that l, KENNETH S. JOHN- SUN, a citizen of the United States, residing at Jersey City, in the county of Hudson, State of New Jersey, have invented certain new and useful Improvements in Signaling Systems, of which the following is a full, clear, concise, and exact description.

This invention relates to circuit arrangements for signaling systems wherein repeat ers or amplifiers are employed.

As is well known in the art, considerable difiiculty is encountered in repeater or amplifier circuits, particularly of the two-way type in preventing the amplifiers "from howling or singing. This ctmdition is due to the fact that part of the amplified energy in the output of the amplifier finds its way back into the input of the amplifier to be re-amplified thereby causing the amplifier to howl or sing. in accordance with this invention, it has been found that this condition may be overcome by associating with the line and the repeater an impedance and a transformer having a plurality of windings so designed that the repeater input circuit and output circuit are conjugate, thereby preventing this feedback of energy while still maintaining a high efiiciency in the system.

It. has been hitherto proposed to prevent this singing by connecting the repeaters between the telephone or signaling lines in a so-called four-wire circuit, two of the wires being employed to repeat in one direction, the other two being employed to repeat in the opposite direction. The arrangenwnt provided in accordance with this invention requires only a three-wire circuit for twoway repeatingbetween lines, and therefore from an economical standpoint has advantagesover the tourwire circuit. also been found that the attenuation for .1 sis is considerably reduced by the employment of a three-wire circuit, an important ad vantage in case the three-wire circuit is electrically long and is used as a trunk line to connect two central telephone stations "tor example. 7

As the line and the repeater may be associated with the trans former and the au'xil iary impedance in a large number of ways to produce the desired result. this invention will, be better understood by reference to the following detailed description taken in corn nection with the accompanying drawings 5, 1919. Serial No. 321,888.

in which Fig. 1 represents this invention applied to a two-way repeating system, in which one amplifieris employed for repeating in both directions. Fig 2 illustrates this invention in connection with a two-way repeater system in which separate amplifiers are employed tor repeating in opposite directions. Fig. 3 is a modification of Fig. 2. F 'ig. l illustrates how additional amplifiers may be inserted between the threewire circuit and the two signaling lines, and Fig. 5 is a modification of Fig. 4;.

In the two-way repeating system illustrated in Fig. 1, two telephone lines 7, S and 9, 1.!) are associated with each other by a three-wire repeater circuit comprising the three-line wires or branches 12, 18 and 14. The central branch 13 includes line 9. ll) and is connected to the common terminal of windings 15 and 16 0t tanstormer 17. Branch 12 contains the output of the amplifier 20 and is connected to a terminal of winding 15. ot' the amplifier 20 and is connected to the winding 16 of transformer 17. Current for the amplifier EEO-is supplied by a battery 24., Inductance 25, which is in series with battery 2-l prevents any substantial amount of the signaling currents from passing throughthe battery. 7

in order toprevent any energy from the output of amplifier 20 from being fed back. into the input side oi the amplifier, windings 15 andlG oi. the transformer snould be so designed with respect to the rest of the circuit that the current through winding induces a counterelectromotive force in winding [(3, equal to the electromotive tori-e impressed thereon due to its conductive connection. By such an arrangement none oi the amplifiei cnergv will iind it way back to the input ot'ihe amplifier to be rcamplified and produce the undersirable elicct known as howling. it has been found that the value of the inductance of these two windings to prevent this howling should S satisfy the following relation, where Branch 1d includes the input too is made to the Campbell Patent- No. l,25-l,-- 4-172 of January 1918, wherein are con-- cidercd substation circuits comprising a line a transmitter, a receiver and an auxiliary in'ipedancc so (ilesigned that they are made anti-side tone.

The operation of the circuit of Fig. l i now be explained as follows. Signals nating 'trom transmitter will induce onding variations in the current flowing througz 'h coils i5 and 16 which are in s ies relation with the input of amplifier These signaling *a 'iations will then he i ,1 5 1"" f) l l' l) lllllllllll u by ampnher .40, and W1 .l e 1m pressed between points 31 and ot th three-wire rircuit, so that they will pas? vl' l J t: l "Jr-'Yl 7 l HA- 7 9:) om on me ano oe en v) y .eeen e1 uu. .llowever none of the amp ified E gnals trom amplifier 20 will pass through branch on account of the previously defined relation. Signals from line 7, 8 will 'theretore be amplified by amplifier 20 without producing any singing in the circuit. Similarly, signals or ginating in transmit will be harnessed between points Eli and 3;? and therefore on the branch 14 which includes in input ot the amplifier. The ampli'lieiil l in branch 12 will be imprt d by rinsiiornier 17 on line 7, S and will he reired by eceiver .536. The three-wire .iit acorn described, therefore repeats in e ther direction without any of the amplified energy heing fed back into the input of the amplifier to produce singing.

:2 the three-wire circuit connected betweciii lines 40 and l1 is similar to that of Fig: 1, except that it CORGI-IDS two amp lilie s. one aunplitying signal originating in line all and the other ampli'lying signals miigiiniting in line 45,. Lines aO-and' all are associated with each other by a reater circuit, comprising the three branches and e25. Branch includes the line it and connected to the common terminal of windings a: and o'l? transformer 49. Connecteiil to the secondary of the trans lornier is at auxiliary impedance 5O. the in of which will be described later include-5 the output of amplifier 5i and is connected to a terminal oi winil'ig li'. Branch to incl es the input of :vzmplilier J nd is =:':.onnec;ui to a to: l ot winding +18. The out-put of 523 is ociatcd with line ll hji in on to present ent r in the output of be" impressed on the i" 52, he associated appara these requirements anipliti ll and 48 equals the product the int pedance of b'anch at times the sell impedance of winding 53. Similarly in order to pretend; any oil. the ainplii'icd encrg" jtroin the output ol' amplitiei- 52 trom he impressed on the input or an'iplztier lit, the

noduct oi the imp nice or line ell times the number of turn i titling in; should. equal, the product or the impcilumzc ct element- 5? times the number of turns in winding 55.

With the apparatus des' 'ncd to meet .il will amplify signals originating in li e l. and will impress them on line 410 without any of the amplified energy tind its way to branch to of the a circuit. Sin'lilarly t-l11'(2\\i1.( signals origil'latillg in line l0 will be amplified by amplifier 52 and impressed on line all without allowing any ot' the amplified energy to tiow through branch 4:25 which includes output of amplifier 5t.

In Fig. 3, lines and till are connected by a three-wire circuit comprising ln'anches (52, 63 and (it. B 'anch 62 includes line (it) and is connected to a terminal or u 'lnl'iing 66 0t transformer 67. Branch (38 includes the input of amplifier (39 and is connecied to the common terminal of u indings {it and T0. Branch (it includes an auix'iliary balancing impedance 71. The output of amplifier (it) is associated with line til by m nus: of a transformer 72. l'unplitier 73 has its output connected to the winding 74- ot' transformer 67. One terminal of the input of amplifier 73 is connected to the common terminal of windings 77, 78 0t transformer T2, other terminal. of the input o'l amplifier 72:) is connected to that terminal o't balancing in1- pedance 80 which is electrically remote from winding 78.

In order to prevent any oi" the an'lplified energy in the output of amplifier 69 from being impressed on the input ol amplifier T3, the product of the impedance of line 61. times the number of turns in winding 78 equals the product of the impedance of element 80 times the number oi turn-- in winding 77. Similarly none oi? the ainrtli lied energy troin amplifier '73 will hr- I pressed on the input. of amplifier 6i .i. in?

product. of the impedance between l e.

(32 and '63 looking in the direction o hue (50 times the number of turns in rcimi equals the product ot' the impedance betwein branches 63 nd 6t looking in the ill-- includes windings 88, 89 of transformers 90, 91 respectively. Branch 86 includes at one end, the input of amplifier 92 and, at the other end, the output of amplifier 93.

ranch 87 includes windings 9 1 and 95. The output of amplifier 92 has one of its terminals connected to the common terminal of windings 95, -96 of transformer 97. The other terminal of the output of amplifier 92 is connected to that terminal of balancing impedance 98 which is electrically remote from winding 96. The input of amplifier 93 is connected to line 83 by transformer 99. The input of amplifier 100 is connected to winding 101 of transformer 91. The output of amplifier 100 is connected to line 83 in a manner similarto the connection of the output of amplifier 92 to line 84. Amplifier 103 has its input connected to a winding of transformer 97 and has its output connected to a Winding of transformer 90.

The following relations must be maintained in order to prevent any of the arm plifiers illustrated in Fig. 4 from singing:

(/1) None of the amplified energy from amplifier 103 will get into the input of amplifier 92 if the product of the impedance between branches S5 and 86 looking in the direction of line 83 times the number of turns in winding equals the product of the impedance between branches 86 and 87 looking in the direction of line 83 times the number of turns in winding 88.

(7)) None of the amplified energy from amplifier will get into the input of amplifier 93, it the product of. the impedance of line 83 times the number of turns in wind- .ing 2- equals the product of the impedance of 1.02 times the number of turns in wind ing 81. 1

(0) None of the output of amplifier 93 will get into the input of amplifier 1.00 it the product of the impedance between branches 85 and 86 looking in the direction of line 8-1 times the number of turns in winding 9% equals the product of the impedance between branches 86 and 87 looking in the direction of line 8d times the number of turns in the winding 89.

(d) The input of amplifier 103 will receive none of the amplified energy from the output of amplifier 92 ii the product of the impedance of line 841- times the number of turns in winding 96 equals the product of the impedance of element 98 times the number of turns in winding 95.

ltlowerer. it is not necessary that'these four conditions be satisfied simultaneously in order to prevent howling in the system oi Fig. 1. for there will be no howling or singing it either condition or condition 7)) and either condition (7)) or (c) are fulfilled.

Signals originating in line 81 will be im' pressed by transformer 97 on amplifier 103. The amplified energy in the output of amplireadily traced, it will be seen that signals originating in line 83 will be successively amplified by amplifiers .3 and 92 and impressed on lineS l without causing any of the amplifiers in the circuit to sing.

In the modification illustrated in Fig. the three-wire circuit is shown to 'be subdivided in order to permit the insertion of additional amplifiers. One part of the threewire circuit comprises branches 10:"). 106 and 1.07; the other part of the three-wire circuit comprises branches 108, 109 and 110. Branch includes winding 111 of transformer 112, a terminal of the input of the amplifier 113, winding, 114, a terminal, of the output of amplifier 113 and winding 115 oi' transformer 1.16. Branch 106 includes the input of amplifier 117 the battery 119 and the output of amplifier 120 and is connected between the common terminal of windings 111. 121 and the common terminal of windings 115 and 122. Branch winding 121, a terminal of the input of the amplifier 113, winding 125, and winding 122. Coils .114 and 125 are of low resistance and are so wound on a. common core as to ofier high impedance to tin-rents which in transmission from the line 150 to line 139 would tend to flow in the outside wires 10.7 and 107 past the connections of said wires to repeater 113, but to ofi'er negligible im pedance to currents which in transmission from line 139 to line 150 flow over wires .05 and 107 in parallel for one side of the line.

Branch 108 includes windings of transformer 116 and winding 131 0'1" transformer 132. Branch 109 includes the input of amplifier 120 and the output of amplifier Brant-h 110 includes winding 130 of transformer 11.6 and winding 137 of transformer 132. The input of amplifier is coni'iected to the telephone line 139 by means of a trans'tormer 138. Connected between windings 157. 158' and windings159. 160 of the secondary o1 trans'tormer 138 is an auxiliary impedance 141. The midpoints of windings 157. 158 and 159. 160 are connected to the output of the amplifier 143. The input of amplifier 143 is connected to a winding of transformer 132. Amplifier 1 15 has its input connected to a winding of a transformer 1 16 and has its output connected to a winding of transformer 11.2. The output of amplifier 117 is connected to line in a manner similar to the connection of the output of amplifier 1413to line 139.

107 in ludes and. 106 looking in tho dirociion oi line lion of line 1.39 times None oi? the amplifiors i ciri. rz'uigement oi? F 1g. 5' will snap; it tho mg relations are maintained:

(a) In order to prevent any energy output of ampllfier 11'. Doing nupressa V I A 139 times the nunihrr o'l turn Winding: 121 equals the product of the in'iuef'lauco tween 1:) anolies 106 and 1i)? looking; in the direct on of line 139 times the numiz-er oi turns in Winding 111.

None of tho output will get into the in iut oi the product of th branches 10R and 1h) in winding 12 0 equals the pr parlance between hranrlws I, ingin the dirrrl'ion lint number of turns in winding 7 will get into tho input of anroli 1131 iii the product of tho inipadzuu-r F-tW-EAii tho neutral hranoh 1m; and the oi id? hraurh lllfi looking" in the dirort on o l lino times tho uun'ihor of turns in winding 12 oquals the product of the 'iuipedanro l .iwran branch 106 and branch 15)? looking); in the direction of line 150 times the number oi turns in Winding 115.

(a) Nour of the output of ain iilifior 1 will he inu irossed on the. input of amplifier 135 if the produrt of the impedance of lino 13.) times the number of turns in windings 158 and 159 equals the produrt oi? the im prdanre of element 111 times tho number m turns in windings 157 and 160.

(f) None of the outputof aniplilier will o impressed on the input oi amplifier 143 ii the product of tho iinpodaiu-o hatwron hraiu'hos H18 and 109 looking" in tl' H tiouoi lino 150 tiu' rs the niuuhor o in handing 137 equals the produrt oi tho iiuprdaurto hatu't-on branches l0!) and 1E!) looking in the dirortiou o'l line @5 1 times tho nuuilwr ol turns in winding 12%.

The OI 'JOX'utiQU oi? the circuit ar *angoineut of Fifi. may then he explaind. as follows.

Si uals originating in line 150 will. he im PYQSSQil on amplifier 1-15 by transfor Th s amplified s1 nals irom amplifier 345 l trom amplifiers and 113 l ns't'ornr rs However none of tho outside hr: nchos through branch 106. After being amplified by amplifier 1155 the si uals are impressed on the substation set which is (20111;: utod to the line 139. By circuits readily traced it will be seen that signals originating in line 13$) will he succas iwol amplified by au1plitiers 185, and 117 hoforo being impressed on line In transmitting from line 150 to line 12% only tho 'lwo outs'lc branches are rmployod, While in transmitting in the ()P JUSllO direction the two outside branches in. parallol 'l orin one side of thev line, the other side of which i ormorlv by the central branch. 7

It is evident that tho principles un lorlyin; the. circuit armugomrnt of Fig. 5 may he applied in casoswhere it desired to employ a larger or smaller uumlzor of aur pliliors between two signaling lines.

The broad. aspect oli this iuvontion has been covered in a separate appliration filed oy his, Serial No. 321,889. tiled September 5, 1 O i It is to he understood that this iuvvntion may or: employed \"nth aiuplii'iors or ropuat 0i": 3 other typos than tho one shown sporifir-iilr in the drawings ahovo dosrrihed.

J1 t claimed is: V 1. In a HljJflilllIlfI systouu two substations,

a lino circuittherohotu'eou romprisiug two outsido liraiinhes and neutral roudurwtiug lniauoh. a line circuitrouiprising two branches between each of sa d suhstations :2 id the respectiie ends of said first line circuit, means for impressing signals from one of: said suhstations tl'u'ough one of? sa d two branch lines upon said tln'ee- -riiiioli line with the two outside branches acting in parallel. the signaling currents returning over the remaining third hraucln ,zuaans tor inr pressing); signals from the other of said suhstitions through its associated t\=.o-lnau(-li upon said three-lu'aurh lino with said :u-tius; serially to tho signailing; rurrouts. and moans nuludod in said. i'l1l,'@0-l)l2l.l}(.'ll line for amplifying tho signals rem. rod from one of said suhstatious.

2, lo a tu'oq ay signal m1. two sulr stz'u'uiuis, a' line circuit coinnrisn 1 two outside branches and a (antral liraiuih. a two hranrh line between each of said suhstations and one end of said first line circuit. CU11- n'octions "whereby signals from one 01 said tWo-hranrh lines are iiupressod on said three branch line with sa d outside braiirh s artin parallel, the signialing currents roturir ing over he remaining third; branch. counections whereby signals from said other twobranch line are impressed on said. threw branch line with said outside branches acting serially, arepeater for impressing on one of said two-branch lines amplified signals from the other two-branch line, said repeater having input terminals and out- -put terminals associated with said threebranch line, and means "for preventing a Substantial amount of energy from said output terminals from being impressed on said input terminals.

- 3. In a two-way signaling system, a line circuit comprising two outside branches and a central branch, a two-branch line circuit connected to said three-branch line at one end thereof, a second two branch line circuit connected to said three branch line circuit at the other end thereof, a repeater having its input terminals connected serially with said central branch and its output terminals associated with one of said two-branch lines, a second repeater having its output terminals coupled to said outside branches in series and having its input terminals associated with said second twobranch line, and means for preventing the output energy of one of said repeaters from being impressed on the input terminals of .said other repeater, while permitting each of said repeaters to impress on one of said two-branch lines amplified signals from the other two'branch line.

4. In a two-way signaling system, a line circuit comprising threebranches, a source of signaling currents, means for impressing currents from said source upon said line with two of said branches acting in parallel,

the currents returning over the third branch, a second source of signaling currents, means for impressing currents from said source upon said line with the two branches acting serially that are employed in parallel for currents from said first source. repeater input terminals and repeater output terminals associated with said three-branch line, said input terminals be ing connected serially to one of said branches said branches having such impedance values that substantially none of the energy from said output terminals is impressed on said input terminals, regardless of the degree of amplification produced by the repeater.

5. In a two-way signaling system, a line circuit comprising three branches. a source of signaling currents, means for impressing currents from said source upon said line :ith two of said branches acting in parallel, the currents returning over the third branch. a second source of signaling currents, means for impressing currents from said source upon said line with the two branches acting serially that are employed in parallel for currents from said firstsource, repeater input terminals and repeater outpi-it terminals associated with said circuit, said output terminals being connected serially to one of said branches, and means for preventing said input termina-ls from receiving any substantial amount of energy from said output terminals, regardless of the degree of amplification produced by said repeater.

6.In a two-way signaling system, two

substations. a line circuit comprising two outside branches and a central'branch, a:

two-branch line between each of said substations'and one end of said first line circuit, an impedance element, said outside branches being serially connected at one end by said element, said central branch inductance, said outside branches being serially connected at one end by said inductance, said central branch being con nected to an intermediate point of said inductance, a repeater having input terminals and output terminals so associated with said circuit that singing of said repeater is prevented regardless of the degree of amplification produced thercby, means for impressing signals from one of said substations on said central branch with said outside branches acting in parallel, and means for impressing signals from said other substation on said circuit with said outside branches acting serially.

8. In a signaling system, two substations, means for providing two-way repeating be tween said substations, said means comprising a three-branch line circuit. means for impressing signaling currents from one of said substations upon said line with two of the branches acting in parallel, the currents returning over the third branch. means for impressing currents from the other substation upon said line with the branches acting serially that act in parallel for currents of the other substation, and an amplifying repeater having input terminals and output terminals so arranged with said line circuit thatsinging of said repeater is prevented regardless of the degree of amplification produced thereby, one kind of said terminals being connected in one of said branches.

9. In a two-way signaling system, a three-branch line circuit, a substation associated with said circuit at each end thereof, means for amplifying signals from one of said'stations, a second means "tor amplifying signals from said other sul'iataticn, connections whereby signals from one oi aid substations are iinpre d on said lirs ampli tyingl'ncans with two branches oi? said line circuit acting parallel, and connections whereby signals from said other subs-la are impressed on said second amplit means with two 0? said branches ac, rially said connections being such that ing of said amplifying means is "prevented regardless of the degree oi am ilitcation produced thereby.

10. In a two-way signaling syst m, two substations line circuit thcrebetween (our prising two outside branches and a central branch, said outside branches being employed in parallel for transn'iission in one direction "between said substations, said outside branches being employed serially for transmission in the opposite direction, a repeaterlhaving its input terminals associated with one of said branches for rcce' ing signals from only one of said SljlbSLtltiOHS, a second repeater having its output terminals associated with another oi? said branches for impressing signals on the other of said substations only, and. means for preventing said input terminals from receiving any substantial amount of energy from said output terminals regardless of the degree of amplification produced by said repeater.

11. In a two-way signaling system, a line circuit comprising two outside branches and a central branch, a source of signaling currents, means for impressing currents from said source upon said line with said two outside branches acting in parallel, the currents returning over said central branch, a

second source of signaling currents, means for impressing currents from said second source upon said line with said two outside branches acting serially, repeater input terminals included serially in said central. branch, repeater output terminals coupled to said. outside branches. said input tern'iinals and said. output terminals being conjugate for all degrees of amplification obtained from said output terminals.

12. In a two-way signaling system, two substations, a line circuit thercltietween com prising two outside branches and a central branch, an impedance element. a second impedance element, said outside branches being serially connected attheir ends by said impedance elei'nents, said central branch being connected. at its ends to intermediate points of said elements, repeater input terniinals included serially in one of said branches, repeater output terminals asso ciated with the other two of said input terminals and said output lierminals being conjugate.

said branches,

ends by said elements, said central path be ing connected to intermediate points of said elements, an amplifier having its input lei" urinals ctmnected serially in said central 1.

path, a second amplifier having its output terminals coupled to one of said elements, means for inipressing signals from one of said substations on said first amplifier, and means for impressing signals from said other substation on said second amplifier.

14;. In a two-way signaling system, two substations, a line circuit comprising two outside branches and. a central conducting path, a two-branch line 'betweenone end of said circuit and one of said substations, a

second two-branch line between the other end of said circuit and said second substation, an inductance, a second inductance,

said outside branches being connected serially at their'cndsby said inductances, said central-path being connected at its ends to in termediate points of said inductances, an am plifier having its output terminals induclively coupled to oneof said inductances, a

from said other two-branch line are impressed on said third amplifier, said connections being such that said third amplifier receives substantially none of the amplified energy fromsaid first two amplifiers.

15. In a two-way signaling systen'i, a two branch line, a second two-branch line, a

threebranch line between said other lines,

an amplifier having its input terminals re- Spons1ve to current flOVlllgSQllflllY through twobranches of said three-branch line, said amplifier having its output circult terminals associated with said first two-branch line for impressing onsaid first twobranch line amplified signals from the second twobranch line, and a second amplifier baring its input terminals responsive to current flowing in parallel through the above mentioned two branches of said three-branch line, said second ampli'fierhaving its output circuit terminals associated with said second two-branch line for impressing onsaid last mentioned line amplified signals from the 16. In a signaling system, two substations, a hne clrcuit comprising two outside branches and a central. conducting path stretchingbetween points geographically remote, a lineeireuit comprising two branches between each of said substations and the re spective ends of said first line circuit, means for impressing signals from one substation serially upon said two outside branches, means for impressing; signaling currents from the other substation through its associated two-branch line upon said first line circuit with said two outside branches acting in parallel, the currents returning over said central conducting path and an ainplifier having input and output terminals for amplifying signals from one of said substations, said input and output terminals being; so connected in said system that said terminals are conjugate regardless of the degree of amplification of said amplifier.

In Witness whereof, I hereunto subscribe my name this 2nd day of September A. D., 2

KENNETH S. JOHNSON. 

